The present invention relates to electrical circuitry for controlling disk rotation, actuator pivoting, data writing and data reading operations within disk drives, and more particularly to a space-saving and efficiency-enhancing arrangement of such circuitry.
In the highly competitive disk drive industry, manufacturers continually strive for improved performance along several fronts. Perhaps best known are the ongoing efforts to increase data storage capacity within given size limits, by increasing the density at which bit-encoded data may be stored. Closely related are the attempts to arrange disk drive components to more effectively utilize available space, either to reduce the size of the drive, or to provide a drive of the same size with increased data storage area, improved operating efficiency, or both. Likewise, components are rearranged in order to achieve more effective dissipation of heat, or to prevent certain components from interfering with one another. Cost reduction efforts include substituting less expensive materials in constructing disk drive components and designing systems in a manner to reduce the time required for manufacturing and testing various disk drive subsystems.
The electrical subsystems of disk drives are subject to the above improvement efforts. These subsystems include circuitry for providing power to rotate the data storage disks and the rotary actuator (to control data transducer position), circuitry for handling servo-signals that control transducing head positions, and circuitry for transmitting signals to record or read bit-encoded data. Traditionally, electrical circuitry including discrete integrated circuit components (e.g. semiconductor chips) and conductive electrical circuit paths interconnecting components, have been supported on a single printed circuit card near the bottom of the disk drive. While satisfactory in many respects, this arrangement has given rise to problems in smaller, more compact disk drive designs. One of these is dissipation of the heat generated by the active circuit components, i.e. the components involved with reading and writing operations and with supplying power to the spindle and rotary actuator motors. Another problem is lack of sufficient space for supporting the circuit components on a circuit card sufficiently small for mounting within a downsized disk drive. The circuit card, when mounted within a drive of a given height, occupies space which otherwise might accommodate an axially extended spindle assembly or rotary actuator. This limits disk drive storage capacity and efficiency.
One modification involves mounting the circuit card at the top of the disk drive, rather than the bottom. This can improve heat dissipation from electrical components mounted above the circuit card, but does not satisfactorily address the other problems.
U.S. Pat. No. 5,038,239 (Vettel et al) discloses a circuit arrangement in which several circuit cards are distributed throughout the disk drive, occupying available space near the top of the drive, along certain side walls, and in a stack of three spaced apart cards occupying open space near the actuator. Flexible cables and connectors are employed to electrically interconnect the circuit cards.
This arrangement, however, is subject to difficulties in reliability and manufacturing cost. The connectors impede the establishment and maintenance of reliable electrical interconnections. These connectors, particularly the high pin count, required have a comparatively high failure rate and are more subject to deterioration and damage from shock and vibrations. The arrangement requires installation of several circuit cards instead of just one, e.g. six separate circuit cards as disclosed in the preferred embodiment. After installation the required flexible circuitry must be plugged into connectors mounted on the circuit cards. The individual circuit cards must be separately tested before installation and interconnection. This of course takes more time, and introduces the possibility of failure due to improper interconnection despite the successful testing of the individual circuit cards. All of these factors add significantly to the time and cost of manufacturing.
Therefore, it is an object of the present invention to provide electrical circuitry for controlling and operating a disk drive, including rigid circuit panels attached to one another in a manner that facilitates their mounting in a non-coplanar arrangement, yet structurally and electrically couples the panels without conventional electrical connectors.
Another object is to provide an electrical circuit arrangement for a disk drive that can be tested as a unit in a substantially planar configuration, then installed as a unit and assume a multi-level or multi-orientation configuration.
A further object is to provide a self-contained circuit arrangement with built-in flexible interconnections of substantially rigid electrical circuit panels, to permit flexibility in the positioning and orientation of the panels relative to one another in a manner that improves disk drive operating efficiency and heat dissipation by integrated circuit components supported by the circuit panels.
Yet another object is to provide a rigid and flexible electrical circuit arrangement that lends itself to strategic positioning of integrated circuit components while maintaining accepted industry standard mounting holes and power and interface connectors, and further allowing clearance for "full height" spindle motors and rotary actuator motors.